1. Field of the Invention
The present invention relates to a medical catheter, and more particularly, but not by way of limitation, to an improved catheter feeding tube having a permanent magnet on the distal end portion so that the distal end portion can be steered within a patient's body by an external magnet. The improvement according to the present invention provides a sensor which, as the external magnet is moved toward the patient's abdomen, indicates the point at which the permanent magnet in the distal end portion of the catheter is captured by the magnetic field of the external magnet. As used herein, the terms captured or capture are used to indicate a condition in which the distal end portion of the catheter will move within the patient's body in response to movement of the external magnet adjacent the patient's abdomen. The term traction position will be used to indicate the farthest position of the external magnet from the catheter distal end portion which results in capture of the distal end portion by the magnetic field of the external magnet.
2. Discussion
U.S. Pat. No. 5,431,640, Gabriel, discloses a method and apparatus for intubation of a patient. A force couple is established between a permanent magnet in the catheter tip and a external permanent magnet. The force couple imparts a traction force to the catheter tip for advancing movement of the catheter tip in the direction of bolus in the stomach beyond the pyloric sphincter and into the duodenum.
The use of magnetic field produced by an external magnet to maneuver a catheter to the distal duodenum of a patient requires precise knowledge of the anatomy of the stomach and duodenum in relation to the abdominal surface of the patient. This knowledge is necessary so the operator can maneuver the external magnet over the abdomen of the patient in a precise path resulting in advancement of the catheter through the stomach and into the duodenum of the patient. An operator maneuvering an external magnet can not see through the abdominal wall to decide whether the distal end portion of the catheter is continuously captured by the magnetic field of the external magnet during the advancement of the catheter. Thus, an additional procedure is required to determine whether the distal end of the catheter is properly advancing into the patient's duodenum.
One method involves the use of X-ray monitoring to confirm the position of the distal end of the catheter. Another method, described in U.S. Pat. No. 5,431,640, requires the aspiration of fluid from the distal end of the catheter and the measurement of the pH of the aspirated fluid. However, pH values for a particular patient may vary from expected values, thereby resulting in false position information. What is needed is an apparatus for advancing the distal end portion of a catheter using the field of an external magnet which provides an indication whether the distal end of the catheter is being properly advanced into the patient's duodenum.